Contra-Rotating Propeller Radial Adjustment for Noise and Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Contra-rotating propeller arrangements face increased noise generation due to stream tube contraction and interaction between propeller blades and vortices, while reducing the diameter of the second propeller assembly to minimize noise can lead to reduced propulsive efficiency.
Innovation Solution
A propeller arrangement with radially extendable and retractable first and second propeller assemblies, where the control system adjusts their diameters relative to each other to optimize noise reduction and efficiency across different flight stages by varying the radial offset between the propeller tips, using a hydraulic or electric control system to manage propeller extension and retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the diameter of the second propeller assembly is reduced to minimize noise generation, then noise generation is reduced, but propulsive efficiency is reduced
Solution Approach 1:
The patent applies the dynamics principle by making the second propeller assembly radially extendable and retractable, allowing its diameter to be dynamically adjusted. During take-off and climb phases, the second propeller retracts radially inward to reduce diameter and avoid vortex interaction, minimizing noise. During cruise phases, the second propeller extends radially outward to increase diameter and maximize propulsive efficiency. This dynamic adjustment resolves the contradiction between noise reduction and efficiency maintenance across different flight conditions.
2Object-generated harmful factors
If the diameter of the second propeller assembly is reduced to have tips radially inward from vortices at all flight conditions, then noise generation is reduced, but the contra-rotating system loses propulsive efficiency
Solution Approach 1:
The patent implements dynamics by enabling the second propeller assembly to dynamically adjust its radial position. The control system commands radial retraction of the second propeller during high-thrust conditions (take-off, climb) when stream tube contraction is greatest and vortex interaction would be most problematic, thereby reducing noise without permanently sacrificing efficiency. During low-thrust cruise conditions, the second propeller extends to restore full diameter and efficiency.
Solution Approach 2:
The patent applies parameter changes by varying the physical parameter of the second propeller assembly's diameter based on flight conditions. The control system monitors flight phase and adjusts the second propeller's radial position accordingly, changing its effective diameter parameter to optimize the balance between noise reduction and propulsive efficiency for each specific operating condition.
3Object-generated harmful factors
If the second propeller assembly has a smaller diameter than the first propeller assembly, then noise generation from vortex interaction is reduced, but the ability to maintain efficiency across varying stream tube contraction is limited
Solution Approach 1:
The patent resolves this contradiction through dynamics by implementing a radially adjustable second propeller assembly that can change its diameter in response to varying flight conditions. The control system detects the current flight phase and commands appropriate radial positioning of the second propeller, enabling the system to adapt between noise-reduction mode (retracted) and efficiency mode (extended) rather than being fixed at a single suboptimal diameter.
Data Source
AI summary
A propeller arrangement has a first propeller assembly providing a row of first propellers, and a second propeller assembly, rearward of the first propeller assembly, providing a row of second propellers. The first and second propellers are radially extendable and retractable. The propeller arrangement further has a control system for controlling the extension and retraction of the first and second propellers. The control system is arranged such that when the propellers of one of the first and second propeller assemblies extend, the propellers of the other of the first and second assemblies retract.